For the analysis and testing of nucleic acid molecules, amplification of a small amount of nucleic acid molecules, isolation of the amplified nucleic acid fragments, and other procedures are necessary. The polymerase chain reaction method is widely used for the amplification of nucleic acid molecules, in which an extremely small number of nucleic acid molecules or fragments can be multiplied by several orders of magnitude to provide detectable amounts of material. On the other hand, isolation and detection of particular nucleic acid molecules in a mixture requires a nucleic acid sequencer and fragment analyzer, in which gel electrophoresis and fluorescence detection are combined. However, electrophoresis becomes very labor-intensive as the number of samples or test items increases. For this reason, a simpler method of analysis using DNA oligonucleotide probes is becoming popular. In this method, many kinds of oligonucleotide probes are immobilized on the surface of a solid to make a probe array. When contacted with a sample, only nucleic acid molecules with specific sequences matching the oligonucleotide are trapped on the surface of the solid and detected.
This kind of isolation and detection method, in which biological probes are immobilized on the surface of a solid and hybridization proceeds between the probes and a sample, has long been known as a blotting method in which the presence of the target molecule is detected by a probe immobilized on a membrane using radioactive labeling. However, immobilization of a large number of probes on a small area has the advantage that only a small amount of sample is required, and a large number of probes can be used simultaneously.
There are several methods for production of such products. Probe molecules can be synthesized one base at a time by a photochemical reaction on small segments of a solid using the same photomasking techniques used in the semiconductor industry. In another method, a synthesized DNA, a PCR-amplified DNA, or a protein molecule is immobilized on a small segment of the surface of a solid for each probe. A third method is to use an inkjet droplet to deposit the biological probe onto the surface. After the biological probes are attached to the surface, the sample containing the target molecule to be analyzed is passed over the biological probes at a temperature conducive to rapid hybridization of the target molecule with the probes. A washing solution then removes all the unhybridized, unbound molecules.
This method requires the use of fluorescent or radioactive labels as additional materials. Such a system is expensive to use and is not amenable to being made portable for biological sample detection and identification. Furthermore, the hybridization reactions can take up to two hours, which for many uses, such as detecting biological warfare agents, is simply too long. Therefore, a need exists for a device and system which can rapidly detect target molecules from samples.
The present invention is directed to achieving these objectives.